有沒有辦法在Haskell的列表中加一個Enum Bounded Ord類型？

Question

我有以下數據類型：

data Suit = Club | Diamond | Heart | Spade 
     deriving (Eq, Ord, Bounded, Enum) 

data Rank = 
R2 | R3 | R4 | R5 | R6 | R7 | R8 | R9 | R10 | 
Jack | Queen | King | Ace 
    deriving (Eq, Ord, Bounded, Enum) 

data Card = Card {suit::Suit, rank::Rank} 
     deriving (Eq, Bounded) 

，現在有[Card]列表。有沒有辦法讓我在列表中加一個Card的Rank？例如給出一個清單[Card Club R2, Card Club R2]我想使它[Card Club R3, Card Club R3]。我寫了下面的代碼：

-- | Update certain number of cards' rank in the list. 
updateRankList :: Int -> [Card] -> [Card] 

updateRankList num (x : xs) 
    | num == 0 = [] 
    | otherwise = updateRank x ++ updateRankList (num - 1) xs 

-- | Update a card's rank, didn't finish. 
updateRank :: Card -> Card 

updateRank card = 

而我卡住了。誰能幫我？謝謝。

Answer 1

你可以做一個包裝SUCC爲界與枚舉類型：

succWrap x = if x == maxBound then minBound else succ x 

，那麼你只需要

updateRanks n xs = map succWrap (take num xs) ++ drop num xs 

Answer 2

:info Enum 

非常有用！我正在尋找的功能是succ，謝謝你們。